//
// Copyright 2013 Google Inc. All Rights Reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// Scopers help you manage ownership of a pointer, helping you easily manage the
// a pointer within a scope, and automatically destroying the pointer at the
// end of a scope.  There are two main classes you will use, which correspond
// to the operators new/delete and new[]/delete[].
//
// Example usage (scoped_ptr):
//
//  {
//      scoped_ptr<Foo> foo(new Foo("wee"));
//  } // foo goes out of scope, releasing the pointer with it.
//
//  {
//      scoped_ptr<Foo> foo;            // No pointer managed.
//      foo.reset(new Foo("wee"));      // Now a pointer is managed.
//      foo.reset(new Foo("wee2"));     // Foo("wee") was destroyed.
//      foo.reset(new Foo("wee3"));     // Foo("wee2") was destroyed.
//      foo->Method();                  // Foo::Method() called.
//      foo.get()->Method();            // Foo::Method() called.
//      SomeFunc(foo.release());        // SomeFunc takes ownership, foo no longer
//                                      // manages a pointer.
//      foo.reset(new Foo("wee4"));     // foo manages a pointer again.
//      foo.reset();                    // Foo("wee4") destroyed, foo no longer
//                                      // manages a pointer.
//  } // foo wasn't managing a pointer, so nothing was destroyed.
//
// Example usage (scoped_array):
//
//  {
//      scoped_array<Foo> foo(new Foo[100]);
//      foo.get()->Method();            // Foo::Method on the 0th element.
//      foo[10].Method();               // Foo::Method on the 10th element.
//  }
//

#ifndef JSTD_SCOPED_PTR_H
#define JSTD_SCOPED_PTR_H

#if defined(_MSC_VER) && (_MSC_VER >= 1020)
#pragma once
#endif

//
// This is an implementation designed to match the anticipated future TR2
// implementation of the scoped_ptr<T> class, and its closely-related brethren,
// scoped_array<T>, scoped_ptr_malloc<T>.
//

#include <stddef.h>
#include <stdlib.h>
#include <assert.h>
#include <cstdlib>      // For std::free()

namespace jstd {

// A scoped_ptr<T> is like a T *, except that the destructor of scoped_ptr<T>
// automatically deletes the pointer it holds (if any).
// That is, scoped_ptr<T> owns the T object that it points to.
// Like a T *, a scoped_ptr<T> may hold either nullptr or a pointer to a T object.
// Also like T *, scoped_ptr<T> is thread-compatible, and once you
// dereference it, you get the thread safety guarantees of T.
//
// The size of a scoped_ptr is small:
// sizeof(scoped_ptr<T>) == sizeof(T *)
//

template <typename T>
class scoped_ptr {
public:
    // The element type
    typedef T element_type;

private:
    T * ptr_;

public:
    // Constructor.  Defaults to initializing with nullptr.
    // There is no way to create an uninitialized scoped_ptr.
    // The input parameter must be allocated with new.
    explicit scoped_ptr(T * p = nullptr) : ptr_(p) { }

    // Destructor.  If there is a C object, delete it.
    // We don't need to test ptr_ == nullptr because C++ does that for us.
    ~scoped_ptr() {
        enum {
            type_must_be_complete = sizeof(T)
        };
        delete this->ptr_;
    }

    // Reset.  Deletes the current owned object, if any.
    // Then takes ownership of a new object, if given.
    // this->reset(this->get()) works.
    void reset(T * p = nullptr) {
        if (p != this->ptr_) {
            enum {
                type_must_be_complete = sizeof(T)
            };
            delete this->ptr_;
            this->ptr_ = p;
        }
    }

    // Accessors to get the owned object.
    // operator* and operator-> will assert() if there is no current object.
    T & operator * () const {
        assert(this->ptr_ != nullptr);
        return *(this->ptr_);
    }
    T * operator -> () const {
        assert(this->ptr_ != nullptr);
        return this->ptr_;
    }
    T * get() const {
        return this->ptr_;
    }

    // Comparison operators.
    // These return whether two scoped_ptr refer to the same object, not just to
    // two different but equal objects.
    bool operator == (T * p) const {
        return (this->ptr_ == p);
    }
    bool operator != (T * p) const {
        return (this->ptr_ != p);
    }

    // Swap two scoped pointers.
    void swap(scoped_ptr & p2) {
        T * tmp = ptr_;
        ptr_ = p2.ptr_;
        p2.ptr_ = tmp;
    }

    // Release a pointer.
    // The return value is the current pointer held by this object.
    // If this object holds a nullptr pointer, the return value is nullptr.
    // After this operation, this object will hold a nullptr pointer,
    // and will not own the object any more.
    T * release() {
        T * retVal = this->ptr_;
        this->ptr_ = nullptr;
        return retVal;
    }

private:
    // Forbid comparison of scoped_ptr types.  If T2 != T, it totally doesn't
    // make sense, and if T2 == T, it still doesn't make sense because you should
    // never have the same object owned by two different scoped_ptrs.
    template <typename T2> bool operator == (scoped_ptr<T2> const & p2) const;
    template <typename T2> bool operator != (scoped_ptr<T2> const & p2) const;

    // Disallow evil constructors
    scoped_ptr(const scoped_ptr &);
    void operator = (const scoped_ptr &);
};

// Free functions
template <typename T>
inline
void swap(scoped_ptr<T> & p1, scoped_ptr<T> & p2) {
    p1.swap(p2);
}

template <typename T>
inline
bool operator == (T * p1, const scoped_ptr<T> & p2) {
    return (p1 == p2.get());
}

template <typename T>
inline
bool operator != (T * p1, const scoped_ptr<T> & p2) {
    return (p1 != p2.get());
}

//
// scoped_array<T> is like scoped_ptr<T>, except that the caller must allocate
// with new [] and the destructor deletes objects with delete [].
//
// As with scoped_ptr<T>, a scoped_array<T> either points to an object
// or is nullptr.  A scoped_array<T> owns the object that it points to.
// scoped_array<T> is thread-compatible, and once you index into it,
// the returned objects have only the thread safety guarantees of T.
//
// Size: sizeof(scoped_array<T>) == sizeof(T *)
//

template <typename T>
class scoped_array {
public:
    // The element type
    typedef T element_type;

private:
    T * array_;

public:
    // Constructor.  Defaults to initializing with nullptr.
    // There is no way to create an uninitialized scoped_array.
    // The input parameter must be allocated with new [].
    explicit scoped_array(T * p = nullptr) : array_(p) { }

    // Destructor.  If there is a C object, delete it.
    // We don't need to test ptr_ == nullptr because C++ does that for us.
    ~scoped_array() {
        enum {
            type_must_be_complete = sizeof(T)
        };
        delete [] this->array_;
    }

    // Reset.  Deletes the current owned object, if any.
    // Then takes ownership of a new object, if given.
    // this->reset(this->get()) works.
    void reset(T * p = nullptr) {
        if (p != this->array_) {
            enum {
                type_must_be_complete = sizeof(T)
            };
            delete [] this->array_;
            this->array_ = p;
        }
    }

    // Get one element of the current object.
    // Will assert() if there is no current object, or index i is negative.
    T & operator [] (ptrdiff_t i) const {
        assert(i >= 0);
        assert(this->array_ != nullptr);
        return this->array_[i];
    }

    // Get a pointer to the zeroth element of the current object.
    // If there is no current object, return nullptr.
    T * get() const {
        return this->array_;
    }

    // Comparison operators.
    // These return whether two scoped_array refer to the same object, not just to
    // two different but equal objects.
    bool operator == (T * p) const {
        return (this->array_ == p);
    }
    bool operator != (T * p) const {
        return (this->array_ != p);
    }

    // Swap two scoped arrays.
    void swap(scoped_array & p2) {
        T * tmp = this->array_;
        this->array_ = p2.array_;
        p2.array_ = tmp;
    }

    // Release an array.
    // The return value is the current pointer held by this object.
    // If this object holds a nullptr pointer, the return value is nullptr.
    // After this operation, this object will hold a nullptr pointer,
    // and will not own the object any more.
    T * release() {
        T * retVal = this->array_;
        this->array_ = nullptr;
        return retVal;
    }

private:
    // Forbid comparison of different scoped_array types.
    template <typename T2> bool operator == (scoped_array<T2> const & p2) const;
    template <typename T2> bool operator != (scoped_array<T2> const & p2) const;

    // Disallow evil constructors
    scoped_array(const scoped_array &);
    void operator = (const scoped_array &);
};

// Free functions
template <typename T>
inline
void swap(scoped_array<T> & p1, scoped_array<T> & p2) {
    p1.swap(p2);
}

template <typename T>
inline
bool operator == (T * p1, const scoped_array<T> & p2) {
    return (p1 == p2.get());
}

template <typename T>
inline
bool operator != (T * p1, const scoped_array<T> & p2) {
    return (p1 != p2.get());
}

//
// This class wraps the c library function free() in a class that can be
// passed as a template argument to scoped_ptr_malloc below.
//

class ScopedPtrMallocFree {
public:
    inline void operator () (void * p) const {
        std::free(p);
    }
};

//
// scoped_ptr_malloc<> is similar to scoped_ptr<>, but it accepts a
// second template argument, the functor used to free the object.
//

template <typename T, typename FreeProc = ScopedPtrMallocFree>
class scoped_ptr_malloc {
public:
    // The element type
    typedef T element_type;

private:
    T * ptr_;

public:
    // Constructor.  Defaults to initializing with nullptr.
    // There is no way to create an uninitialized scoped_ptr.
    // The input parameter must be allocated with an allocator that matches the
    // Free functor.  For the default Free functor, this is malloc, calloc, or
    // realloc.
    explicit scoped_ptr_malloc(T * p = nullptr) : ptr_(p) {}

    // Destructor.  If there is a C object, call the Free functor.
    ~scoped_ptr_malloc() {
        this->reset();
    }

    // Reset.  Calls the Free functor on the current owned object, if any.
    // Then takes ownership of a new object, if given.
    // this->reset(this->get()) works.
    void reset(T * p = nullptr) {
        if (this->ptr_ != p) {
            FreeProc free_proc;
            free_proc(this->ptr_);
            this->ptr_ = p;
        }
    }

    // Get the current object.
    // operator* and operator-> will cause an assert() failure if there is
    // no current object.
    T & operator * () const {
        assert(this->ptr_ != nullptr);
        return *(this->ptr_);
    }

    T * operator -> () const {
        assert(this->ptr_ != nullptr);
        return this->ptr_;
    }

    T * get() const {
        return this->ptr_;
    }

    // Comparison operators.
    // These return whether a scoped_ptr_malloc and a plain pointer refer
    // to the same object, not just to two different but equal objects.
    // For compatibility with the boost-derived implementation, these
    // take non-const arguments.
    bool operator == (T * p) const {
        return (this->ptr_ == p);
    }

    bool operator != (T * p) const {
        return (this->ptr_ != p);
    }

    // Swap two scoped pointers.
    void swap(scoped_ptr_malloc & b) {
        T * tmp = b.ptr_;
        b.ptr_ = this->ptr_;
        this->ptr_ = tmp;
    }

    // Release a pointer.
    // The return value is the current pointer held by this object.
    // If this object holds a nullptr pointer, the return value is nullptr.
    // After this operation, this object will hold a nullptr pointer,
    // and will not own the object any more.
    T * release() {
        T * tmp = this->ptr_;
        this->ptr_ = nullptr;
        return tmp;
    }

private:
    // no reason to use these: each scoped_ptr_malloc should have its own object
    template <typename T2, typename GP>
    bool operator == (scoped_ptr_malloc<T2, GP> const & p) const;

    template <typename T2, typename GP>
    bool operator != (scoped_ptr_malloc<T2, GP> const & p) const;

    // Disallow evil constructors
    scoped_ptr_malloc(const scoped_ptr_malloc &);
    void operator = (const scoped_ptr_malloc &);
};

template <typename T, typename FP>
inline
void swap(scoped_ptr_malloc<T, FP> & a, scoped_ptr_malloc<T, FP> & b) {
    a.swap(b);
}

template <typename T, typename FP>
inline
bool operator == (T * p, const scoped_ptr_malloc<T, FP> & b) {
    return (p == b.get());
}

template <typename T, typename FP>
inline
bool operator != (T * p, const scoped_ptr_malloc<T, FP> & b) {
    return (p != b.get());
}

} // namespace jstd

#endif // JSTD_SCOPED_PTR_H
